Abstract : The author in 1956, during a study of flora and vegetation on Bol'shoy Lyakhovskiy Island, collected material giving some idea on the subterranean structure of the phytocoenoses in the arctic tundra. These data were obtained for the polygonal moss-herb tundra and for the hillocky-spotted grass-woodrush-willow (salic polaris)-moss tundra in digging up the root systems, drawing their horizontal and vertical placement and in determining the bulk of subterranean organs according to the various horizons of the soil profile. (Author)